1. Technical Field
The present invention relates to improving the aging characteristics of automobile components. More specifically, the invention relates to a method and arrangement for limitation of at least one controllable operating parameter that can cause ageing of at least one component or one material arranged in connection with an engine.
2. Background Art
In the field of motor vehicles such as passenger cars, various components occasionally gradually impair due to, among other things, ageing and wear. In order to prevent or delay ageing and the consequential non-functional ability of a certain component too early in the life cycle of a vehicle or the component, limits are commonly defined for certain operating parameters during operation of the vehicle. In doing so, the component in question can be protected and its life cycle enhanced.
One example of a component that is exposed to ageing and impairment, and therefore the risk of non-functioning, is an exhaust manifold arranged in connection with a combustion engine. The exhaust manifold guides exhaust gases out of the combustion engine to the environment by way of a rear exhaust system. Due to ageing and occasionally high temperatures, the exhaust manifold may be gradually subjected to disintegration and impaired function. In order to reduce the risk of non-functioning of the exhaust manifold, a limitation can be defined with respect to the temperature of the exhaust gases that flow out of the engine and through the exhaust manifold. In this manner, a premature impairment of its function is prevented.
According to known techniques, this exhaust gas temperature limitation can be accomplished by limiting engine output power or by limiting the supply of a rich fuel mixture to the engine. This can be controlled by a computer-based control unit available for the vehicle in question. However, one drawback regarding this method is that the maximum limit allowed for the exhaust gas temperature must be broadly set so that the worst possible operating situation is taken into consideration. For example, one such extreme operating situation occurs when a particularly active driver frequently drives the vehicle at very high loads and engine speeds. Thus, the limitation regarding exhaust gas temperature is broadly set so that functional incapability does not occur prematurely. Since limiting exhaust gas temperature requires a greater fuel supply, a limitation with a wide safety margin results in a comparatively high fuel consumption for the vehicle, which is a drawback.
As another example, it is known that motor oil in a combustion engine gradually degrades, particularly due to driving with comparatively high engine speeds and high torque from the engine. In this case, limiting the risk of impairment of the motor oil can be accomplished by maximizing the engine speed. This maximization can be accomplished by a computer-based control unit. More precisely, compulsory control of the engine speed is such that it never exceeds a certain limit corresponding to the risk of motor oil impairment. However, such a method can involve a drawback in the form of a perceived impaired performance of the vehicle.
One additional vehicle component where a similar limitation of a functional incapability is relevant is an exhaust catalyst. This is because the catalytic active surface of the exhaust catalyst decreases with age. Therefore, in order to insure that the exhaust catalyst function is not impaired prematurely, it is known to limit the temperature of the exhaust gases flowing through the exhaust catalyst.
Another operating parameter which can be limited in a vehicle is its output torque. According to European Patent No. 0507500, the output torque of an engine can be limited if certain predetermined parameters, such as the level and temperature of the coolant, the pressure and temperature of the motor oil, and the temperature of the air flowing into the engine, differ from certain predetermined limit values.
A primary object of the present invention is to provide an improved method for limitation of controllable operating parameters that can cause ageing of engine components and materials arranged in connection with an engine. This object can be accomplished by a method of continually determining a value that corresponds to the degree of impairment of the component or material affected by aging. This method includes determining a maximum limit value that is allowed with respect to at least one operating parameter, wherein the determination depends upon the continuously determined value. The object is also accomplished by an arrangement for limitation of at least one controllable operating parameter that can cause ageing of at least one component or one material in connection with an engine.
The invention provides a method for limiting at least one controllable operating parameter that can cause ageing of at least one component or one material associated with an engine. The method includes determining a maximum limit value allowable with respect to the operating parameter, and controlling the engine so that the limit value is not exceeded, thereby limiting ageing of the component or material. The invention includes continuously determining a value corresponding to the degree of impairment of the component susceptible to or affected by ageing, wherein the determination of the limit value is made depending on the corresponding value.
Accordingly, the present invention is able to establish for at least one component a limitation of a predetermined, controllable operating parameter in the engine or the vehicle which causes ageing of that component or a certain material with the intention of limiting the ageing as well as determining the risk of functional incapability of that component or the material in question. Since this limitation is dependent on the degree of ageing for a given component and material, respectively, the present invention is able to improve the emissions, the fuel consumption and the performance of the vehicle.
Other advantageous embodiments of the invention will be apparent from the appended claims.